In ink-jet printing methods, droplets of ink are directly projected onto a printing medium from very fine nozzles and allowed to adhere to the printing medium to form characters or images thereon. The ink-jet printing methods have now been extensively employed not only in printing applications for ordinary consumers but also recently in commercial and industrial printing applications because of easiness of full coloration and adaptability for production of a small number and many kinds of printed materials.
In the commercial and industrial printing applications, for example, there has been proposed a high-speed printing method in which a rolled synthetic resin film is scanned using a stationary printing head of a line printing type.
For example, in Patent Literatures 1 and 2, there have been proposed the ink-jet printing methods in which a high-quality printed material having color images noticeable on a white background is obtained by printing such color images on a surface of a resin sheet or a rolled resin film.
JP 2008-200850A (Patent Literature 1) discloses an ink-jet printing method including the steps of forming a non-white pattern layer on a surface of a transparent film substrate, and then forming a white solid image printing layer on the non-white pattern layer, in which a resolution of the aforementioned non-white pattern layer is higher than a resolution of the white solid image printing layer.
JP 2013-10364A (Patent Literature 2) discloses an ink-jet printing method including the steps of printing a print unit constituted of a white solid image printing layer and a non-white pattern layer on a surface of an elongated transparent film substrate using two liquid ejection means, in which after forming the non-white pattern layer and then drying the non-white pattern layer, the white solid image printing layer is formed on the thus dried non-white pattern layer.
In addition, JP 2014-94495A (Patent Literature 3) discloses an ink-jet printing method that is capable of printing images having excellent rub fastness and excellent peeling resistance, said method including the steps of allowing droplets of a white-based ink composition containing a urethane-based resin to adhere to a printing surface of a soft packaging film to print white-based images thereon, allowing droplets of a color ink composition to adhere to the thus formed white-based images to print color images thereon, and heating the white-based images and the color images at a temperature of higher than 40° C. In Patent Literature 3, as the heating means, there are illustrated forced air heating, radiation heating, electric conduction heating, high-frequency drying and microwave drying.